1. Field of Invention
Exemplary aspects of the present invention relate to optical modules and optical transmission devices having a vertical-cavity surface-emitting laser (VCSEL).
2. Description of Related Art
In related art optical fiber communications systems, multimode optical fibers that have a larger core diameter than that of singlemode optical fibers and provide easy optical coupling with a light source are often used in short distance data communications up to about several hundred meters, and referred to as LAN (Local Area Network) and SAN (storage area network).
When communicating with a multimode optical fiber, degradation of the S/N ratio called mode selection loss poses a problem. In order to enhance mode selection loss, in the related art, the use of a light source whose emission light has a low coherence is effective. For example, according to Laid-open Patent Application HEI 7-170231, transmission distance of several hundred meters is secured in high-speed data communications at 1.5 Gbps or more by using a VCSEL (vertical-cavity surface-emitting laser) of a multimode oscillation as a light source.